This invention relates to a multi-chip package (MCP) semiconductor device wherein a plurality of semiconductor elements are encapsulated within a single body of resin.
While it is desired to make semiconductor device of one chip in order to make an electronic system employing such a semiconductor device high in packaging density and speed, it takes a prolonged term for designing, developing and delivering new semiconductor devices. Also, many problems concerning the electrical characteristics and wafer processing must be solved in order to realize a combination of an analogue circuit and a digital circuit. Therefore, instead of the system on chip arrangement, a semiconductor device of the multi-chip package (MCP) type in which a plurality of presently available semiconductor chips are encapsulated within a single package is being increasingly used.
One example of the conventional MCP-type semiconductor device includes a ceramic substrate or a printed circuit board on which a plurality of semiconductor chips are mounted and which is transfer molded together with a lead frame. However, since this arrangement utilizes a ceramic substrate or a printed circuit board both of which are expensive, the overall device is expensive.
In another conventional MCP-type semiconductor device, a plurality of semiconductor elements are directly mounted to a lead frame as illustrated in FIGS. 14 and 15. That is, in these figures, the semiconductor device comprises semiconductor elements 3 respectively mounted on two substantially rectangular die-pads 2 each having two supporting leads 1. The die-pads 2 are arranged in a side-by-side relationship to each other and a number of leads 4 are disposed around the die-pads 2 so that their inner ends may be connected by bonding wires 6 to the electrodes 5 on the semiconductor elements 3. As illustrated in FIG. 16, the electrodes 5 on the neighboring sides of the semiconductor elements 3 are electrically connected together by bonding wires 7, whereby the number of the leads 4 is reduced and the package substrates may be simplified. The whole assembly thus prepared is encapsulated within a single resin 8 except for outer portion of the leads 4.
In the conventional MCP semiconductor device as above described, the leads 4 can be freely arranged only at around the periphery of the die-pads 2, so that the electrical connection between the electrodes 5 on the semiconductor elements 3 and the leads 4 cannot be freely arranged, requiring the number and the length of the leads 4 to be increased, the overall dimensions of the MCP semiconductor device to be increased and the lead inductance to become high.
Also, since the electrodes 5 on two different semiconductor elements 3 are connected together by bonding wires 7 as illustrated in FIG. 16, which causes the semiconductor element 3 to receive a large mechanical stress through the electrode 5 on the stitch bond side 9 of the bonding wire 7 at which the bonding wire 7 is firmly pressed against the element 3 and severed, the reliability of the semiconductor element 5 is decreased. Also, the only electrodes 5 that can be connected together by the bonding wires 7 are those on the neighboring sides of two semiconductor elements 3.